David Hughes is the Daily Telegraph's chief leader writer. He has been covering British politics for 30 years.

Ed Balls cannot believe his luck

Ed Balls is positively cock-a-hoop over the latest Tory statistical blunder. The Opposition show-cased its report on teen pregnancies with the claim that 54 per cent of teenage girls in deprived areas get pregnant. That figure was wrong by a factor of 10 – the real rate is 5.4 per cent. Never one to resist a serious gloating opportunity, the Schools Secretary went to town. These "dodgy statistics", he said, showed the Tories would stop at nothing "to talk Britain down". They are so "out of touch with family life in Britain that they believe over half of teenage girls in the poorest areas fall pregnant… how low can David Cameron go?…smears and distortions", etc etc etc. Forget Balls' synthetic outrage for a moment. What will really delight him is just how ragged the Tory back office operation seems to be. There are supposed to be some bright brains servicing the Conservative machine but blunders like this suggest otherwise. This is not a one-off, either. Earlier this month Chris Grayling , the shadow home secretary, was rebuked by Sir Michael Scholar, head of the UK Statistics Authority, for "damaging public trust in official statistics" by using crime figures tendentiously. It's time Tory HQ introduced more rigorous quality control on its data. No wonder Balls is chortling.